Wolf, are you there?
While the return of wolves poses real difficulties for farmers, the presence of this carnivore can also have ecological and societal benefits. Jean-Louis Martin, a researcher at the Center for Functional and Evolutionary Ecology (CEFE), explains.
© Matthieu – stock.adobe.com
Slowly but surely, wolves are making a comeback. While they have remained relatively abundant in Canada and Alaska, there are now nearly 6,000 of them in the United States, south of the Canadian border. In Western Europe, the wolf population is estimated at over 12,000, including 500 in France. In fact, wolves never really went very far... "This is a natural colonization of French territory from Italy, which is home to one of the population centers that remained in Europe," explains Jean-Louis Martin.
Colonization is often viewed through the prism of the serious difficulties posed to farmers: "The negative effects of the presence of wolves on livestock farming, such as the number of sheep killed, are visible and easy to prove,"explains Jean-Louis Martin. On the other hand, the potential benefits that wolves could bring from an ecological or civic perspective are often indirect and very difficult to demonstrate..."To better visualize these advantages and disadvantages, the researcher and his colleagues have published a summary of the issues raised by the coexistence of deer, wolves, and humans. We learn that while the return of the wolf poses problems, it is also likely to bring advantages...
Regulating deer populations
For if the wolf is returning, it is certainly because it is now protected, but also because the past century has seen a spectacular increase in the number of deer and roe deer, the carnivore's prey of choice. "While these large herbivores have been reintroduced in some areas, they have also naturally colonized new territories," says the ecologist. However, this "successful" return is not without ecological and societal consequences.
Left to their own devices, ungulates can cause real devastation to forests. "In studies we conducted in Canada, we showed that in the absence of deer predators, 90% of the undergrowth vegetation disappeared."As a result, many invertebrates that live in these undergrowth areas disappear in turn, followed by the birds that feed on them.
The thousands of teeth of these herbivores also limit the regeneration of young trees, while their hooves trampling the forest promote soil compaction. "In France, the damage caused by deer to agriculture was estimated at around €20 million in 2004,"says Jean-Louis Martin.
Cohabitation, Road Safety, and Health
And that's not counting the economic and human costs caused by... road accidents. In 2012, there were 1.23 million road accidents involving deer in the United States, killing 200 people and causing $4 billion in damage. Every year in Germany, 200,000 deer collide with vehicles, causing 50 deaths and 3,000 injuries, with an estimated total repair cost in Europe of more than €1 billion, including €100 million in France. "Some recent studies suggest that the return of deer predators could lead to a decrease in the number of deaths resulting from these collisions," says the researcher.
Finally, the return of the wolf would have positive effects on... human health. Deer and roe deer are indeed a prime vehicle for ticks, whose nymphs are carriers of diseases that can affect humans. "A significant decrease in the density of deer can thus reduce the incidence of Lyme disease," concludes Jean-Louis Martin.
"Be careful, this is not about demonizing deer or sanctifying wolves," warns Jean-Louis Martin, "but simply about taking a broader view of the consequences of the presence of wolves in a context where their wild prey is abundant, and helping to improve coexistence between wolves, deer, and humans." The researcher conveyed this message earlier this year to the Minister for Ecological and Solidarity Transition as part of the work of the scientific council on wolves and livestock farming.
Upward or downward control?
Why is the world green? Researchers offer two possible answers to this question. The first hypothesis is that the world is green because plants use "strategies" such as thorns or toxic molecules to prevent herbivores from eating them completely. This is known as the bottom-up control hypothesis. The second hypothesis is that the world is green because herbivores, anxious to escape their predators, spend a lot of time managing this risk of predation and devote less time to feeding, consuming only the bare minimum without devouring the forests. This is known as the top-down control hypothesis.
To test these hypotheses, researchers turned to a life-size laboratory: an archipelago in Canada where some islands were colonized by deer and others remained free of these large herbivores. "We found that in the absence of their predators, deer clear the undergrowth of vegetation and cause a decline in biodiversity," explains Jean-Louis Martin, a result that in this case is consistent with the hypothesis that top-down control of herbivores is necessary to keep the world green.
Hence the ecological importance of wolves, bears, cougars, lynxes, wolverines, and other large carnivores. "If we promote a world without predators, we are removing something that has played an essential role in shaping life as we know it." If just one species is missing, everything is disrupted.